/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.nifi.nar;

public class NarLoaderHolder {

    private static volatile NarLoader INSTANCE;

    public static void init(final NarLoader narLoader) {
        if (INSTANCE == null) {
            synchronized (NarLoader.class) {
                if (INSTANCE == null) {
                    INSTANCE = narLoader;
                } else {
                    throw new IllegalStateException("Cannot reinitialize NarLoaderHolder");
                }
            }
        } else {
            throw new IllegalStateException("Cannot reinitialize NarLoaderHolder");
        }
    }

    public static NarLoader getNarLoader() {
        if (INSTANCE == null) {
            synchronized (NarLoader.class) {
                if (INSTANCE == null) {
                    throw new IllegalStateException("NarLoaderHolder was never initialized");
                }
            }
        }

        return INSTANCE;
    }

    // Private access
    private NarLoaderHolder() {

    }
}
